Already cats wander all over the place and can have inbedded transponders and magnetic "keys" on their collars that open cat flaps. This idea is to use them to pass messages within local communities in a secure, if prehaps haphazard, manner local to the area.

You put the message (with routing information
and maybe some extra logic) into the "cat communication device" (CCD) and let it wander. Other CCDs and receivers at cat flaps and other locations both receive the messages so they can be relayed and exhanged as appropriate. These messages would end up local people's PCs and other computing devices to be read by humans or they could solict an automatic response from a connected facility.

This way a cat could change your newspaper order at your local newsagent, pass a message to a friend or further a debate on local issues. As a side effects you could discover the range of your cat and find out what other CCD-enabled cats it encounters in the course of it's day. This is fairly safe legally in the UK as owners are not responsible for their cats other than their obligation to look after them responsibly and not cause a nuisence or health hazard by keeping too many.

The problem with this is that cats are territorial. A cat will generally stick to its own territory, only venturing into other cats' territories if it believes it can challenge the other cats for them. Thus cats are unlikely to go through other cats' cat flaps, or even rub against public transponders (cats only rub against objects they mark as being of their own territory).

I was hoping that they would exchange messages with each other and with receivers on proximity. I often find local cats staring at each other, probably giving enough time for a swift data exchange. Also this way you could be part of the network if cats regularily walk past the window at the front of your house as you could place a transceiver there. Maybe where I am in the UK there are just too many cats as there are always different cats wandering about the street, doing various things, at all hours of the day.

why not?
i think its about time cats evolved past the territorial level and took some public responsability instead of lounging around all day, chasing smaller members of their food chain or scratching the upholstery. maybe you could get thomas the bacardi breezer cat to front the movement; his media skills and popularity would be a great bonus to the cause.

Carrier pidgeon protocol has both been suggested here and exists already is prepared (spoof) internet draft proposal format. The key difference is that cats wander around without any discernable purpose while homing pidgeons go rapidly from place to place. It is probably worth noting that the cat community network would probably interfer with the pidgeon protocol by causing packet loss.

wasquake: Sounds like you have a enviroment that restricts the range of this protocol. Maybe it could provide a home intranet service for you. The cat meows at you, you authorise it for food with a widget and when it goes into the kitchen a device reads your authorisation in the CCD and food is automatically dispensed.

The good thing about cats is that they have a entirely seperate view of territory to people. This means they wander wherever they want - a similiar protocol technique would be use to balls given to children to spread messages between back gardens. However cats wander about themselves, not needing small children as means to transfer them from one garden to another.